Where can I change the background color of the notification in the Info header?
To my knowledge it cannot be changed, it is defined by the Box group in the User Interface tab. The only bits of it I could change were the border color and the gradient. The text color is changed globally it seems.

One workaround you could use is to tick the shaded check box and set both values to 100, this gives a bright white which might help against a darker color.

Default


Brighter